The background of the invention will be set forth in two parts.
1. Field of the Invention
This invention relates to microwave systems and more particularly to passive components utilized at relatively high signal levels.
2. Description of the Prior Art
It has been observed that various components of a microwave system which are normally considered to be passive can exhibit nonlinear effects at high signal levels. This was brought out, for example, in an article by R. D. Cox entitled "Measurements of Waveguide Component and Joint Mixing Products in 6 GHz Frequency Diversity Systems", in IEEE Transactions on Communication Techniques, Vol. COM - 18, No. 1, February 1970, pp. 33-37.
These effects are manifest in the generation of intermodulation products and/or the generation of harmonics. Even though the levels of the signals generated are usually very low, they may create severe interference problems in high sensitivity systems that are presently in use or being designed. Up until the present discovery, these nonlinear effects have been considered to be primarily caused by a small but finite nonlinear impedance occuring at mechanical junctions within the microwave device. Other sources of spurious signal generation that have been considered are gaseous condition, thermal condition modulation and thermoelectric junctions. Numerous assembly and fabrication techniques have been employed with moderate success to minimize the generation of these spurious signals.
In contrast to the direction taken in the prior art to overcome this serious problem, the invention recognizes the source of spurious signal generation as the interaction of the local r.f. magnetic fields with the magnetic moments associated with the atoms of the various metals used in fabricating the r.f. structures.
It should, therefore, be evident that a new technique which was not heretofore contemplated in solving this longstanding serious problem would constitute a significant advancement in the prior art.